Touch sensor systems, such as touch screens or touch monitors, can act as input devices for interactive computer systems used for applications such as information kiosks, computers, order entry systems for restaurants, video displays or signage, mobile devices, etc. Touch sensor systems or touch screens may be integrated into a computing device, thus providing interactive touch capable computing devices, including computers, video displays or signage, or mobile devices.
The dominant touch sensor technologies are resistive, capacitive, and acoustic. Acoustic touch sensors, such as ultrasonic touch sensors using surface acoustic waves, are particularly advantageous when the application demands a very durable touch sensitive surface and minimal optical degradation of the displayed image.
Many types of acoustic touch sensors exist. For example, one type of acoustic touch screen includes a touch substrate having an array of transmitters positioned along a first peripheral surface of a substrate for simultaneously generating parallel surface bound or plate waves that directionally propagate through the panel to a corresponding array of detectors positioned opposite the first array on a second peripheral surface of the substrate. Another pair of transducer arrays is provided on the substrate surface at right angles to the first set. Touching the substrate surface at a point causes an attenuation of the waves passing through the point of touch, thus allowing interpretation of an output from the two sets of transducer arrays to indicate the coordinates of the touch. This type of acoustic touch position sensor is shown in WO 94/02911 (Toda), incorporated herein by reference.
Another example of an acoustic touch sensor system, termed the Adler-type acoustic touch screen, efficiently employs transducers, by spatially spreading the signal and analyzing temporal aspects of perturbation as indicative of position. A typical rectangular touch screen thus includes two sets of transducers, each set having a different axis aligned respectively with the axes of a physical Cartesian coordinate system defined by a substrate. An acoustic pulse or pulse train is generated by one transducer, propagating as, e.g., a narrow Rayleigh wave along an axis which intersects an array of reflective elements, each element angled at 45° and spaced corresponding to an integral number of wavelengths of the acoustic wave pulse. Each reflective element in the array reflects a portion of the wave along a path perpendicular to the axis, across a broad touch region on the front surface of a substrate adapted for touch sensing, to an opposing reflective array and transducer which is a mirror image of the first array and transducer, while allowing a portion to pass to the next reflective element of the array. The transducer of a mirror image array receives an acoustic wave consisting of superposed portions of the incrementally varying wave portions reflected by the reflective elements of both arrays, directed antiparallel to the emitted pulse. The acoustic waves are thus collected, while maintaining the time dispersion information which characterizes the coordinate position from which an attenuated wave originated. Wave paths in the active region of the sensor have characteristic time delays, and therefore a wave path or wave paths attenuated by an object touching the touch sensitive region may be identified by determining a timing of an attenuation in the composite returning waveform. A second set of arrays and transducers are provided at right angles to the first, and operate similarly. Since the axis of a transducer corresponds to a physical coordinate axis of the substrate, the timing of an attenuation in the returning wave is indicative of a Cartesian coordinate of a position on the substrate. The coordinates are determined sequentially to determine the two dimensional Cartesian coordinate position of the attenuating object. The system operates on the principle that a touch on the surface attenuates surface bound or plate waves having a power density at the surface. An attenuation of a wave traveling across the substrate causes a corresponding attenuation of waves impinging on the receive transducer at a characteristic time period. Thus, the controller need only detect the temporal characteristics of an attenuation to determine the coordinate position. Measurements are taken along two axes sequentially in order to determine a Cartesian coordinate position. It is also known to take advantage of acoustic wave guiding effects to reduce border widths in Adler-type touch screens. See, U.S. Pat. Nos. 4,642,423; 4,644,100; 4,645,870; 4,700,176; 4,746,914; Re. 33,151; and 6,636,201; each incorporated herein by reference.
These examples of acoustic touch systems typically have a large number of operative elements (either multiple transducers, or a transducer and reflective array) disposed on, and along, the surface of the substrate. In order to prevent damage due to exposure from the environment or external objects, these peripheral operative elements are hidden and protected by a bezel provided over these elements on the front surface of the substrate and sealed, so that only the active touch region on the surface of the substrate is exposed for possible touch input. These types of acoustic touch systems also are limited to processing touch inputs only for the active touch region, which is the part of the transparent touch sensor that is overlying the display under the touch sensor.
In the commercial market for touch system devices, the cosmetic look of the devices as well as the robustness and reliability of feature capabilities of such devices is becoming increasingly important. Various attempts have been made, for example, to minimize the size of the bezel on the periphery of the touch screen in such devices. However, touch devices conventionally still have had a bezel on the front of the device, although the bezel may have been reduced in profile and/or had a thinner border width.
Therefore, it is desired to have bezel-less acoustic touch systems that provide additional touch function features beyond those provided in the active touch region.